Acadia National Park, Maine (AP Photo/Robert F. Bukaty)

Muir Woods National Monument, Marin County, Calif. (AP Photo/Eric Risberg)

Estate Maho Bay, the U.S. Virgin Islands National Park (AP Photo/Steve Simonsen/ The Trust for Public Land)

Grand Prismatic Spring, Yellowstone National Park, Wyoming (CC BY: Frank Kovalchek)

The Dry Tortugas islands, off the coast of Florida, as seen from above (AP Photo/NASA)

Zabriskle Point, Death Valley National Park, California (REUTERS/Lucy Nicholson)

Margerie Glacier, Glacier Bay, Alaska (CC BY: Frank Kovalchek)

Grand Canyon National Park, Arizona (CC BY: Stuart Seeger)

Joshua Tree National Park, California (CC BY: Esther Lee)

Oxbow Bend, Grand Teton National Park, Wyoming (CC BY: Ralph Arvesen)

Bryce Canyon, Utah (CC BY: Frank Kovalchek)

Gates of the Arctic National Park and Preserve, Alaska (CC BY: National Parks Service/Zak Richter)

Great Smoky Mountains National Park, North Carolina (CC BY: Bruce Tuten)

A lunar eclipse is framed within Turret Arch at Arches National Park, Utah (AP Photo/Julie Jacobson)